Transfer of cryogenic liquids

ABSTRACT

This invention relates to a system which permits the storage and transfer of cryogenic fluids without losses due to handling and venting and which is characterized by reversed-cascade filling procedure. This system for transfer of a cryogenic liquid from a supply container to a receiver is characterized in that only a single fluid connection is made between the container and receiver without venting the receiver so that the receiverfilling operation may be achieved without gas or liquid loss by evaporation or overflow as by the use of a submerged and continuously primed pump.

United States Patent [72] Inventors Cleve C. Kimmel Torrance; John H.Moll, Hawthorne, both of Calif. [21] App1.No. 819,681 [22] Filed Apr.28, 1969 [45] Patented Jan. 1 1, 1972 [73] Assignee Parker-HnnnifinCorporation Cleveland, Ohio [54] TRANSFER OF CRYOGENIC LIQUIDS 9 Claims,2 Drawing Figs.

[52] U.S. Cl 62/49, 62/52, 62/55 [51] Int. Cl. Fl7c 7/02 [50] Field ofSearch 62/45, 55, 49

[5 6] References Cited UNITED STATES PATENTS 2,487,863 11/1949 Garretson62/54X 2,610,471 9/1952 Thayer 62/55 X 2,964,916 12/1960 Keeping 62/55 X2,964,918 12/1960 Hansen et al. 62/55 X 2,993,344 7/1961 Reed 62/55 X3,191,395 6/1965 Maher et a1 62/54 3,260,061 7/1966 Hampton et al. 62/55X 3,262,280 7/1966 Chaney 62/49 Primary ExaminerAlbert N. Davis, Jr.Att0rney-Oberlin, Maky, Donnelly & Renner ABSTRACT: This inventionrelates to a system which permits the storage and transfer of cryogenicfluids without losses due to handling and venting and which ischaracterized by reversed-cascade filling procedure. This system fortransfer of a cryogenic liquid from a supply container to a receiver ischaracterized in that only a single fluid connection is made between thecontainer and receiver without venting the receiver so that thereceiver-filling operation may be achieved without gas or liquid loss byevaporation or overflow as by the use ofa submerged and continuouslyprimed pump.

TRANSFER OF CRYOGENIC LIQUIDS BACKGROUND OF THE INVENTION Aircraft arenow being equipped with inerting systems for fire and explosionprevention and for fire extinguishment which comprise dewars containingan inert cryogenic liquid such as N for release into fuel tank or otherspaces which may contain combustible or explosive liquids or vapors.Accordingly, there is presented the problem of periodic refilling of theaircraft dewars.

ln known transfer equipment, cryogenic liquid is transferred from asupply container to a vented receiver thus resulting insubstantial lossof liquid by evaporation and overflow. Various practices sometimesprovide complex transfer equipment such as an auxiliary tank and pumpbetween the supply containers and the receiver, a vapor bleed-offmechanism, and several fluid interconnecting lines to effect transfer.

SUMMARY OF THE INVENTION Contrary to the foregoing, the transfer ofcryogenic liquids herein from a ground supply dewar to an aircraft dewarinvolves only the connection of a flexible supply hose from the supplydewar to the disconnect coupling of the aircraft dewar, the latter asaforesaid, being the inert gas supply source for the aircraft inertingsystem.

One object of the present invention is to provide for cryogenic liquidtransfer from a supply dewar to an aircraft dewar without venting of thelatter and without overflow, whereby there is no evaporation loss of theliquid nor is there any possibility, in the case of liquid N of erosiveor other damage to concrete pavement and the like due to overflow.

Another object of this invention is to provide for a transfer ofcryogenic liquids, such as N which entails the use of but a single fluidline connection between the supply dewar and the aircraft dewar, thesupply dewar cart or trailer having the necessary control equipment toobtain desired automatic filling of the aircraft dewar with cryogenicliquid at predetermined saturated vapor pressure and to predeterminedlevel.

Another object of this invention is to provide for the transfer ofcryogenic liquids which utilizes a pump means between the supply dewarand the aircraft dewar, and an intervening heat exchanger which assuresfilling of the aircraft dewar to a predetermined-saturation level formost effective use in inerting the fuel tank and other spaces of anaircraft.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic drawing of apreferred embodiment of the invention wherein an aircraft dewar issupplied with cryogenic liquid from a portable supply dewar; and

FIG. 2 is a similar schematic drawing illustrating a modificationwherein a heat exchanger in an emergency application is substituted forthe pump means of FIG. 1 to discharge liquid from the supply dewar.

DISCUSSION OF THE INVENTION Referring to FIG. 1, the ground supply unit1 may constitute a cart or trailer which carries thereon a supplycontainer 2, i.e., a vacuum-insulated, double-wall dewar, a centrifugalpump 3, a heat exchanger 4, valves 5, 6, and 7, a thermal sensor unit 8,and an operating unit 9.

The outlet of the supply dewar 2 is connected to the inlet of pump 3 byconduit and the outlet of said pump 3 is connected to the disconnectcoupling 11 by conduit 12 via the check valve 13, the control valve 5,the mixing valve 7, and the thermal sensor unit 8. A bypass conduit 14has therein the heat exchanger 4 and the control valve 6 whereby aportion of the pump discharge may be heated as hereinafter described indetail.

The airplane 15 has therein an aircraft dewar 16 having an outletconduit 17 leading to the inerting system via a shutoff valve 18. Afilling conduit 19 leads from the disconnect coupling 11 to a spraydevice 21 disposed within said dewar l6 and above the filling levelswitch 23 which has its electrical lead 24 plugged into a socket element25 in the lead 26 of the operating unit 9. A relief valve 27 in conduit19 is set to relieve vapor pressure in aircraft dewar 16 exceeding apredetermined maximum. When the dewar 16 is to be filled a flexible hose28, preferably of vacuum evacuated, double-wall construction, isconnected to the disconnect coupling 11.

In normal operation the saturated vapor pressure in the aircraft dewar16 operates at a predetermined level that is greater than the saturatedvapor pressure in the supply dewar 2. In the event that the pressure indewar 16 is higher than the predetermined level, this pressure must bereduced.

To fill the dewar 16, the flexible hose 28 is connected to thedisconnect coupling 11 and the socket 25 is plugged into lead 24 of thelevel switch 23. The operating unit 9 is then actuated to the "fillposition to open control valve 5. If the pressure in the aircraft dewar16 is higher than predetermined, control valve 29 is opened to allow thepressure to decrease. The operating unit 9 is provided with apressure-actuated interlock 30 arranged to turn on the pump drive motor31 when the pressure in the aircraft dewar 16 has reached thepredetermined level, and when the pump 3 is driven it draws liquid fromthe supply dewar 2 and pumps it through the conduit 12, valves 5 and 7,thermal sensor unit 8, hose 28, and conduit 19 into the vapor space ofthe aircraft dewar l6. Initially, the conduit 12 and hose 28 between thesupply dewar 2 and aircraft dewar 16 is somewhat warm and heat will betransferred to the liquid as it flows to the dewar 16. This causes thegas pressure in the space of the dewar 16 to start to increase at thetime that the pump 3 is started. However, this flow action is followedby some liquid carried along with the gas and the two phase mixtureenters the dewar 16 through the spray device 21 whereby the amount ofgas initially introduced is rechilled by the cold walls of the dewar 16and by the vapor therein.

The pressure increase at startup peaks out just below the reliefpressure of the relief valve 27 and at this point liquid droplets startto enter the dewar 16 to cause a pressure collapse of the vapor therein.The pressure decay continues and when it drops below the predeterminedsaturated level as pressure or temperature sensed by the thermal sensorunit 8, the latter is activated to position the control valves 5 and 6so that some of the liquid delivered by the pump 3 is conducted throughthe heat exchanger 4, whereby the heated liquid passes through thecontrol valve 6 to mix in the mixing valve 7 with the liquid passingthrough the other control valve 5. The filling rate is preferably suchthat the thermal heat gain in the liquid between the thermal sensor unit8 and the dewar 16 is insignificant so that the sensor unit 8constitutes a fairly accurate measurement of temperature of the liquidflowing into the dewar 16. Generally, the allowable range of saturationcontrol of the liquid is wide enough so that additional controls are notrequired. However, should the range be relatively small such as, say, 5p.s.i., the thermal sensor unit 8 may be installed in or adjacent thedewar 16 in which case, the signal to the control valves 5 and 6constitutes a signal indicating the precise temperature in or adjacentthe dewar 16.

When the level of the cryogenic liquid in the dewar reaches the levelswitch 23, the indicating light 32 is turned on, and the pump drivemotor 31 is deenergized and the control valves 5 and 6 are closed,whereby no further liquid is supplied from the supply dewar 2 to theaircraft dewar 16. At that time, the operating unit 9 may be shiftedfrom fill to stop and the electric plug-in and fluid disconnectcouplings 25 and 11 may be separated, and as evident, the disconnectcoupling 11 may be provided with self-sealing valve units to preventescape of vapor or liquid.

As shown in FIG. 2, if the ground supply unit 1 is not provided with apump 3, discharging pressure on the liquid in the supply dewar 33 may begenerated by opening solenoid valve 34 for flow of liquid through apressure build up coil 35 into the top of the supply dewar 33 so thatthe increased vapor pressure on the liquid constitutes a pump means forforcing the liquid through the common discharge conduit 12. This method,of course, decreases the thermal efficiencies of the system when used incontinuous operation.

As evident from the foregoing, there is but a single fluid lineconnection 28 between the ground supply cart 1 and the aircraft dewar 16through which the latter is filled to a predetermined level ascontrolled by the level switch 23 and to predetermined saturation levelas determined by the thermal sensor unit 8 whereby the saturated vaporpressure in the dewar 16 will be at a predetermined magnitude.

When the aircraft dewar 16 has thus been filled, the supply hose 28 andelectrical lead 26 may be disconnected from the aircraft and theaircraft is ready for takeoff. The pressurization of the fuel by N andthe supply of N for other uses on the aircraft is not restricted orimpaired by the servicing.

We, therefore, particularly point out and distinctly claim as ourinvention:

1. A system for transfer of a cryogenic liquid from a closed supplycontainer into a closed receiver adapted to contain residual liquidtherein at a temperature greater than that of the liquid in saidcontainer; conduit means between said container and receiver throughwhich liquid from said supply container is introduced into saidreceiver; means establishing a pressure differential between saidcontainer and the vapor space of said receiver to effect flow of liquidfrom said container into said receiver without venting of the latter;and temperature control means in said conduit means operative tomaintain the vapor pressure at a predetermined level in said receiverwhich is greater than the saturated vapor pressure of the liquid in saidcontainer.

2. The system of claim 1 wherein said means establishing a pressuredifferential comprises a pump in said conduit means to establish apressure differential for flow of liquid from said container into saidreceiver.

3. The system of claim 1 wherein said means establishing a pressuredifferential comprises a pump and drive means therefor; wherein valvemeans between said supply container and the portion of said conduitmeans downstream of said pump opens communication between said supplycontainer and receiver in response to vapor pressure in the latterexceeding a predetermined value thus to decrease such vapor pressure;and wherein a pressure actuated interlock energizes said drive means inresponse to decrease of such vapor pressure to predetermined value thusto drive said pump for flow of liquid from said container into saidreceiver.

4. The system of claim 1 wherein said temperature control meanscomprises a heat exchanger and a sensor unit therefor through whichliquid may be conducted to increase the saturated vapor pressure in saidreceiver to predetermined level.

5. The system of claim 1 wherein said temperature control meanscomprises a thermal sensor unit; a heat exchanger; and valve meansoperative to divert a portion of the liquid flowing in said conduitmeans through said heat exchanger for heating thereof and for mixing ofthe heated liquid with the unheated portion of the liquid; said sensorunit actuating said valve means upon decrease of vapor pressure in saidreceiver below a predetermined value.

6. The system of claim 1 wherein said means establishing a pressuredifi'erential comprises a heat exchanger through which a portion of theliquid from said supply container is conducted and supplied therefrom tothe vapor space of said supply container thus to effect flow of liquidfrom said supply container into said receiver.

7. The system of claim 1 wherein said conduit means terminates in spraymeans operative to break up liquid as it enters the vapor space of saidreceiver.

8. The system of claim 1 wherein relief valve means exposed to vaporpressure in said receiver relieves vapor pressure in said receiver whenit exceeds a maximum pressure greater than said predetermined level.

9. The system of claim 2 wherein check valve means in said conduitrneans downstream of said ump prevents reverse flow of liquid in saidconduit means rom said receiver into said supply container.

2. The system of claim 1 wherein said means establishing a pressuredifferential comprises a pump in said conduit means to establish apressure differential for flow of liquid from said container into saidreceiver.
 3. The system of claim 1 wherein said means establishing apressure differential comprises a pump and drive means therefor; whereinvalve means between said supply container and the portion of saidconduit means downstream of said pump opens communication between saidsupply container and receiver in response to vapor pressure in thelatter exceeding a predetermined value thus to decrease such vaporpressure; and wherein a pressure actuated interlock energizes saiD drivemeans in response to decrease of such vapor pressure to predeterminedvalue thus to drive said pump for flow of liquid from said containerinto said receiver.
 4. The system of claim 1 wherein said temperaturecontrol means comprises a heat exchanger and a sensor unit thereforthrough which liquid may be conducted to increase the saturated vaporpressure in said receiver to predetermined level.
 5. The system of claim1 wherein said temperature control means comprises a thermal sensorunit; a heat exchanger; and valve means operative to divert a portion ofthe liquid flowing in said conduit means through said heat exchanger forheating thereof and for mixing of the heated liquid with the unheatedportion of the liquid; said sensor unit actuating said valve means upondecrease of vapor pressure in said receiver below a predetermined value.6. The system of claim 1 wherein said means establishing a pressuredifferential comprises a heat exchanger through which a portion of theliquid from said supply container is conducted and supplied therefrom tothe vapor space of said supply container thus to effect flow of liquidfrom said supply container into said receiver.
 7. The system of claim 1wherein said conduit means terminates in spray means operative to breakup liquid as it enters the vapor space of said receiver.
 8. The systemof claim 1 wherein relief valve means exposed to vapor pressure in saidreceiver relieves vapor pressure in said receiver when it exceeds amaximum pressure greater than said predetermined level.
 9. The system ofclaim 2 wherein check valve means in said conduit means downstream ofsaid pump prevents reverse flow of liquid in said conduit means fromsaid receiver into said supply container.